1. Field of the Invention
The present invention relates to a relay device, and in particular to a relay device which load balances or provides redundancy.
Recently, with developments of communication technology, information transmitted includes voices, static images, video contents, and the like, in which such a multimedia traffic transmission requires a high reliability. In order to secure the high reliability, the redundancy and the load balancing are important in a network.
2. Description of the Related Art
FIG. 11 shows a network using prior art relay devices 110_1, . . . , and 110_n, which forms a group of them (hereinafter, occasionally represented by a reference numeral 110) connected to the same transmission line which connects a communication device 200_1 to a communication device 200_2.
Each of the relay devices 110 is provided with a mutual monitor functional portion, a redundant reception functional portion, and a relay functional portion (not shown). Among these, the mutual monitor functional portion of the relay device 110_1, for example, monitors the states of the other relay devices 110 within the group. When determining that its own device has the highest preference (priority) within the relay devices 110 which are in a normal condition the relay device 110_1 notifies the fact to the redundant reception functional portion of its own device.
Based on this notification, the redundant reception functional portion receives a packet, and the relay functional portion relays this packet according to preset path information.
In this network configuration, only the single relay device 110_1 receives and relays packets during normal times while other relay devices 110_2-110_n assume an unavailable state. Namely, packets are concentrated on the relay device 110_1, and they can not be balanced with the other relay devices 110_2-110_n.
Thus, since data (packets) to be relayed concentrate on a single relay device, packets which can not be relayed will result. Also, as for load balancing by a hot standby configuration, it can not be performed on the same communication path.
FIG. 12 shows a network in which the load balancing is performed by arranging a load balancer 400 between a communication device 200 and relay devices 120_1-120_n.
Since the single load balancer 400 changes a transmitting destination based on a source address and a destination address of a packet, this network is not configured redundantly.
Also, in the prior art duplex operation method for communication protocol processor, the communication protocol processor is connected to a control processor such as a switchboard, adopts a synchronization method by a flag pattern as a data link layer protocol, uses a procedure for communicating by a frame having a link identifier, has a duplex configuration, and accommodates a line into which a plurality of data links are multiplexed. This communication protocol processor is provided with first means by which an input side of each of the communication protocol processors from the line inputs the same frame to both systems and an output side of each of the communication protocol processors in both systems to the line transmits the frame multiplexed, and second means by which only a transmission/reception operation is made an enabling/disabling state per data link by the control processor's instructions. By the second means, half of the data links accommodated in the communication protocol processor is made a transmission/reception enabling state, and the other half is made a transmission/reception disabling state in one system. In the other system, states of the transmission/reception operation are made so as to reverse the states of the above system. Thus, the duplex communication protocol processor is operated in both systems, and processing of whole data links is performed by load balancing (see e.g. patent document 1).
This case also requires the first means (frame multiplexer 23) for multiplexing frames and for transmitting the frame to the output side, and a control processor 1 for providing instructions to the second means.
Patent Document 1:
Japanese Patent Application Laid-open No.6-37865 (pages 2-3 and FIG. 1)
In the network shown in FIG. 11 using such prior art relay devices, although the network is redundantly configured, load balancing is not enabled, a load is concentrated on a single relay device, and data which can not be relayed will result. Also, in the network shown in FIG. 12, although to load balancer 400 is required for the load balancing, the network is not redundantly configured. Also, in the processor shown in the Japanese Patent Application Laid-open No. 6-37865, the frame multiplexer and the control processor are required for the load balancing.